The transgene is composed the 5' Tal1 enhancer element (from -7 to -0.9 kb relative to the transcription start site in exon 1a), the SV40 minimal promoter, and the Cre-ERT cassette, including a rabbit Beta-globin intron. The enhancer element drove endothelial-specific expression of the transgene. Cre was active in the presence of tamoxifen.